Wireless communications systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power). Examples of such multiple-access systems include code-division multiple access (CDMA) systems, time-division multiple access (TDMA) systems, frequency-division multiple access (FDMA) systems, and orthogonal frequency-division multiple access (OFDMA) systems. Generally, a wireless multiple-access communications system may include a number of base stations, each simultaneously supporting communication for multiple user devices. Base stations may communicate with user devices on downstream and upstream links. Each base station has a coverage range, which may be referred to as the coverage area of the base station or cell.
User devices that are proximate to each other may also communicate directly via device-to-device (D2D) communication. D2D communication is carried out using specifically-allocated D2D discovery resources. Before a user device can participate in D2D discovery, however, the user device first acquires the D2D discovery resources allocated to the user device.